Content management solutions facilitate the creation, storage, retrieval, promotion (e.g., through a review/approval and/or other business process or work flow), retention, migration, and/or destruction of content, typically in the context of a relatively large body of content. A content management system typically uses a database, such as a relational database management system (RDBMS), to store metadata associated with content items (e.g., documents or other files or objects) under management of the content management system. In a typical content management system, content items of a particular type may be represented in metadata by a metadata object of a corresponding type, instances of which share methods and/or attributes applicable to content items of that type. For example, a base class “document” may be sub-classed to create a sub-class for documents that are “contracts”. The sub-class may have attributes, such as “contract termination date”, that do not apply to other types of document. Such a type may be further sub-classed, for example to create a type corresponding to a particular type of contract, such as “lease”. In a typical content management system, attributes of object instances of a particular type may be stored in a single database table. If a type is changed in a manner that adds a new attribute or modifies a characteristic of an existing attribute, typically database schema changes are required to reflect the change, including with respect to existing instances, even if the existing instances do not have a value for any new and/or modified attributes.